This invention relates to the adhesive bonding of articles together, and, more particularly, to a bonded structure having high conductivity between the bonded articles.
Many infrared and other types of sensors operate most efficiently when cooled to a cryogenic temperature, such as about the boiling point of liquid nitrogen, 77 K. To effect this cooling in service, the sensor is mounted within a vacuum dewar. The dewar typically includes an insulated housing having a window through which the sensor views an external scene. The electronic component which includes the sensor is supported on one end of a thermally conductive support in a facing relation to the window.
When the sensor is to be operated, the opposite end of the support is cooled by contacting it with either a cold gas or a cryogenic liquid such as liquid nitrogen. Heat flows from the electronic component, through the support, and thence into the heat sink represented by the cold gas or cryogenic liquid. The electronic component, including the sensor, is cooled to the operating temperature of about that of the heat sink.
In this dewar structure, the electronic component must be mechanically affixed to the support with sufficient attachment strength that it can withstand accelerations and loads imposed during service, but in such a manner as to achieve good thermal conductivity from the electronic component to the support and thence to the heat sink. The conventional approach for bonding uses a filled adhesive such as a filled resin or a filled grease. The "filler" is particles of a thermally conductive material such as silver, which increase the effective thermal conductivity of the mixture of filler and adhesive to a value greater than that of the adhesive alone. For example, silver-filled epoxies having thermal conductivities greater than those of unfilled epoxies are available commercially and are used for this application.
The filled adhesive positioned between the electronic component and the support bonds the two together but also acts as a thermal barrier to the flow of heat from the electronic component to the heat sink. The greater the thermal barrier, the lower the rate at which the electronic component and its sensor may be cooled to the service operating temperature, a serious concern for many applications where the sensor must be rapidly cooled from room temperature to the operating temperature. Thus, there is a need for an affixing approach that has good mechanical bonding properties and has a greater thermal conductivity than available with the present approach. The present invention fulfills this need, and further provides related advantages.